Known systems for determining the speed of internal combustion engines typically utilize a clock for determining the amount of time required for cylinder events to occur. As used herein, the term "cylinder event" means, for example, two successive top dead center (TDC) pulses from a crankshaft or camshaft position sensor or other type of engine position sensor. Of course, other convenient crankshaft locations may be used as a reference point. With prior art systems, inaccuracies are encountered at high engine speed because there is a reduction in the resolution of the speed measurement arising from the fact that fewer clock timer counts are accumulated in the common event that the time for only a single cylinder event is used to calculate engine speed. U.S. Pat. No. 4,527,248, illustrates a system having a fixed sampling time interval resulting in a deficiency in accuracy at lower engine speeds.
A system and method according to the present invention overcomes the problems of the prior art by using a predetermined minimum time base for calculating engine speed and engine acceleration. This predetermined minimum base assures that an accurate reckoning of engine cylinder events may be made, so as to provide accurate engine speed and acceleration data.